Cutting tools having helical cutting edge s have been utilized for many years. Though the most common of these tools is the helical drill, helical edges have also been disposed upon other cutting tools, such as milling, grooving, and other cutting inserts, in order to take advantage of the increased cutting surface that a helical edge provides.
A helix is defined as a three-dimensional curve that lies on a cylinder or cone such that its angle to a plane perpendicular to the axis of the cylinder or cone is constant. When applied to a cutting insert, a helix is a function of the start angle at the point along the edge that the helix begins, the helical radius, the length of the arc through which the helix travels, and the finish angle at the point along the edge that the helix ends. Because of the three dimensional nature of a helical edge, conventional two dimensional grinding techniques have not been readily suited for producing helical edges on cutting inserts.
The problem of grinding a three dimensional form on a surface is readily solved by utilizing a computer numerically controlled (CNC) grinder. To grind such a surface utilizing a CNC grinder, one needs to program the travel of the grinder relative to the stationary workpiece, fixture the workpelace within the grinder, and allow the grinding wheel to travel through the preprogrammed helical arc to produce the desired helical surface. However, the application of a CNC grinder to solve the helical grinding problem is not without its drawbacks. First, CNC grinders are very expensive, currently costing between one hundred and fifty and two hundred and fifty thousand dollars. Second, CNC grinders require skilled programmers to program the correct surface equations to yield the desired helical surface. Finally, CN(C grinders are expensive to maintain and run due to their heavy reliance on electronics. Thus, there is a need for a way to grind a helical edge on a cutting insert that is relatively inexpensive to manufacture, does not require the services of skilled programmers to produce a helical edge, and that is relatively inexpensive to maintain and run.
Another method of producing a helical edge on a cutting insert involves the use of a grinding fixture having a specially formed cam to move the workpiece through the predetermined helical arc relative to a stationary grinding wheel to provide the desired helical surface. Such cam guided grinding fixtures are common in the field of helical drill sharpening and are readily adaptable to grinding helical surfaces on cutting inserts. Such a fixture would be relatively inexpensive to manufacture, would not require the services of a skilled programmer to provide the helical edge and would be relatively inexpensive to maintain and run. However, because specially formed cams are utilized in these fixtures, each fixture may only be used to grind a specific helix oil a specific insert. Because of their insert specific nature, cam guided fixtures are undesirable in situations where a variety of inserts and/or helical surfaces is to be ground. In addition, the rotational way in which a cam guided fixture transfers the cam shape to the insert precludes the use of such fixtures on inserts requiring the grinding of compound shapes. Because of this preclusion, such fixtures are not suitable for use with inserts having chamfers, flats or non-rotationial angular surfaces that interact with the helical surface to form such a compound shape. Therefore, there is a need for a way to grind a helical edge on a cutting insert that may be readily adapted to grinding a variety of helical surfaces on a variety of cutting inserts and is adapted to grind compound surfaces having at least one helical surface as a component.
An apparatus for grinding a helical edge on a cutting insert that is relatively inexpensive to manufacture that does not require the services of skilled programmers, that is relatively inexpensive to maintain and run. that may be readily adapted to grinding a variety of helical surfaces on a variety of cutting inserts, and is adapted to grind compound surfaces having at least one helical surface as a component, is not known in the art.